The only RELIABLE way to do this is to have a GPS and Loran right next to each other as you navigate to your TD's with the Loran and then make a new waypoint on your GPS. None of the tools for converting are going to be very accurate.
That said, here's the USCG tool for conversions. Use at your own risk.
Amdren software is the most accurate conversion I have seen for converting loran to GPS. I have the info somewhere around here in fact I have the system. Its out of Florida. Its Amdren software company. 906 S. Ramona Dr. Indialantic, Florida 32903. Its not too expensive either. Im sure they are on the net.
Andren software has a special subroutine which will accurately make the loran to gps conversion, if you have a local waypoint at which you simultaneously measure both loran readings and lat/lon readings. You enter both readings, and the Andren program will then calculate a correction factor which it applies to all the other conversions in the area. This solves the problem which most people have with getting accurate conversions. Using the programs that are included with some GPS units has resulted in waypoints which are close to 1/2 mile off for me.
i think the owner is carl. don't try an order from the list of dealers - none of them have it. they claim to have a better program but it is not calibrated for out area. it took me 10 calls before i got carl on the phone. evenings seem to be best. i ordered it yesterday. will cost you about $80 with shipping.